1. Field of the Invention
The present invention relates to novel diorganopolysiloxanes comprising benzalmalonate functional groups.
2. Description of the Prior Art
It is known to this art to modify diorganopolysiloxanes, whether along the polymer backbone and/or at the end of a polymer chain, by incorporating various organic functional groups therein, with a view towards imparting specific properties to such silicone polymers.
A convenient technique for introducing these organic functional groups is to carry out a hydrosilylation reaction between a diorganopolysiloxane bearing at least one SiH group and an ethylenically unsaturated organic compound bearing in the presence of a catalytically effective amount of a catalyst containing platinum.
Exemplary of such prior art are:
(i) U.S. Pat. Nos. 2,970,150 and 4,160,775, describing the addition of allyl or methallyl alcohol to a silane or diorganopolysiloxane bearing at least one SiH group;
(ii) U.S. Pat. Nos. 3,767,690 and 4,503,208, describing diorganopolysiloxanes bearing groups containing an acrylate or methacrylate functional group;
(iii) U.S. Pat. No. 4,640,967, describing diorganopolysiloxanes bearing an epoxy and/or acrylate or methacrylate group and their use as compositions for coating optical fibers;
(iv) Patent EP-A-0,088,842, describing diorganopolysiloxanes bearing benzophenone groups;
(v) U.S. Pat. Nos. 4,316,033 and 4,373,060 describe alkoxysilanes bearing a benzotriazole functional group F. These patents describe the cohydrolysis of these functional silanes with colloidal silica and an alkyltrialkoxysilane to prepare a silicone resin, namely, a polymer essentially consisting of the units Q(SiO.sub.2), T(CH.sub.3 SiO.sub.1.5) and less than 2 mole % of FSiO.sub.1.5. This silicone resin, cured, is employed as a coating for surfaces made of plastic; and
(vi) U.S. Pat. Nos. 4,404,257, 4,242,381 and 4,242,383 describe polycarbonate compositions containing organic benzylidenemalonate derivatives.
Nonetheless, these patents neither describe nor suggest the preparation of linear or cyclic diorganopolysiloxanes containing a benzylidenemalonate functional group.